Crosslinkable adhesive silicone composition comprising as gelling agent a compound with cyclic amine function borne by a siloxane chain

ABSTRACT

The invention relates to a crosslinkable adhesive silicone composition of the type of those comprising a polyorganosiloxane (POS) comprising Si-Vi units (α,ω-di-Vi-polydimethylsiloxane); a crosslinking POS comprising SiH units; a platinum catalyst; a filler; and optionally an adhesion promoter comprising vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxy-silane and butyl titanate and/or a crosslinking inhibitor and/or an unsaturated POS resin of the MM Vi DD Vi Q or MD Vi Q or MM Vi Q type. This composition is characterized in that it additionally comprises a polyorganosiloxane having, per mole, at least one piperidinyl functional group.

The field of the present invention is that of silicone elastomercompositions which can be crosslinked by addition and/or condensation.The polyorganosiloxanes (POS) considered are of the room temperaturevulcanizable (RTV) type, it being known that, conventionally, they areprovided in the form of two-component systems (RTV-2), the vulcanizationof which, in the case of crosslinking by addition, can be, according tothe use, accelerated with heat.

These products are particularly known for their applications in thefield of moulding and of reproduction; they can then be formed bycasting, injection moulding, deposition with a brush, spraying, and thelike, according to the use.

In the context of the present invention, interest is more particularlydisplayed in self-adhesive silicone elastomer compositions whichcrosslink by an addition reaction and which exhibit modified Theologicalproperties.

More specifically still, the present invention is targeted atcrosslinkable adhesive silicone elastomer compositions comprising athixotropic agent of type: POS comprising a piperidinyl functionalgroup, which confers a high yield point on these compositions. The term“yield point” is understood to mean the ability of a product not to flowspontaneously under its own weight.

Adhesive silicone elastomer compositions of the RTV type are now wellknown and have formed the subject of various applications. Thus, the useof such compositions for the adhesive bonding of various substrates, ofelectrical/electronic components or of mechanical components, inparticular in the motor vehicle field or domestic electrical appliancefield, is known. Such a composition, exhibiting good stability onstorage, a viscosity in the liquid form appropriate for the requirementsof ease of application on the substrates to be adhesively bonded, a highadhesiveness, good behaviour with regard to temperature and goodstability of the adhesiveness over time, while having a low cost price,is disclosed in Patent FR-A-2 775 481.

While this composition proves to be an adhesive silicone composition ofchoice for the abovementioned applications, it does not exhibitTheological characteristics entirely suited to certain specificapplications (non-drip device, seal shaped in place, and the like) wherethe method of deposition requires a yield point of the product.

By analogy with moulding applications, it would then be necessary to addthixotropic additives to the composition in order to make it possible tothicken, to the correct extent, silicone elastomer compositions without,however, affecting their malleability, their fluidity necessary for thehandling thereof, and so that the composition, before crosslinking, doesnot flow spontaneously if this is not required.

Mention may be made, as thixotropic agent, of:

-   -   an ultrafine silica in an appropriate proportion;    -   hydroxylated and aminated additives.

However, depending on the situation, these additives have totallyunacceptable disadvantages.

The disadvantage of the silicas is that they result in a great increasein both the yield point and the viscosity.

The problem of the hydroxylated and aminated additives is that they donot bring about the increase in the yield point desired for all thetypes of compositions of the field. Furthermore, the aminatedderivatives inhibit the action of the platinum catalysts used in thesilicone compositions which can be crosslinked by addition.

Thus, an object of the present invention is to develop a siliconecomposition which can be crosslinked to an elastomer which exhibitsrheological properties perfectly suited to allowing the composition tobe used with success both for the adhesive bonding of various substratesand for carrying out moulding operations requiring non-flowingmaterials.

Another object is to obtain a non-flowing composition which can becrosslinked by polyaddition and, in addition, which can be self-adhesivein the case of adhesive bonding applications.

In addition, in the context of the use thereof in adhesive bonding, thecomposition according to the invention must make it possible to obtain afirm combination which withstands weak stresses, this being the casefrom the time of its instalment (adhesive bonding between thesubstrates). It must also make it possible to obtain good stability ofthe adhesiveness over time.

Furthermore, in the context of the moulding and adhesive bondingapplications, another object is to obtain a composition which can beeasily formed and which is capable of retaining the form thus fashionedat least for the time necessary for the crosslinking. Finally, thiscomposition must retain good mechanical properties and a satisfactorythermal behaviour.

To achieve these objects, the inventors have had the credit ofdemonstrating, in an entirely surprising and unexpected way, that theuse in a crosslinkable silicone composition of a compound comprising atleast one cyclic amine functional group carried by a siloxane chaingreatly increases the yield point of the composition.

The inventors are all the more worthy of credit since they havecountered the preconception according to which aminated compounds areconventionally inhibitors of platinum-based compounds advantageouslyused to catalyse the crosslinking of silicone compositions by addition.

Thus it is that the present invention satisfies the abovesaid objects,among others, by providing, first, a crosslinkable adhesive siliconecomposition of the type of those comprising:

-   -   (I) at least one polyorganosiloxane exhibiting, per molecule, at        least two alkenyl groups bonded to the silicon,    -   (II) at least one polyorganosiloxane exhibiting, per molecule,        at least three hydrogen atoms bonded to the silicon,    -   (III) a catalytically effective amount of at least one catalyst        composed of at least one metal belonging to the platinum group,    -   (IV) optionally an adhesion promoter,    -   (V) an inorganic filler,    -   (VI) optionally at least one crosslinking inhibitor,    -   (VII) optionally at least one polyorganosiloxane resin carrying        Q and/or T siloxyl units and alkenyl groups,    -   this composition also comprising:    -   (VIII) at least one compound comprising at least one cyclic        amine functional group carried on at least one siloxane chain,        as thixotropic additive which modifies the Theological        properties of the composition by conferring thereon a high yield        point.

Preferably, the cyclic amine functional group is a piperidinylfunctional group.

Advantageously, the compound (VIII) is a polyorganosiloxane having, permolecule, at least one unit of general formula: $\begin{matrix}{(R)_{a}(X)_{b}{{Z{Si}}(O)}_{\frac{3 - {({a + b})}}{2}}} & (I)\end{matrix}$in which:

-   -   the R symbols are identical or different and represent a        monovalent hydrocarbonaceous radical chosen from alkyl radicals        having from 1 to 4 carbon atoms, the phenyl radical and the        3,3,3-trifluoropropyl radical;    -   the X symbols are identical or different and represent a        monovalent radical chosen from a hydroxyl group, a linear-or        branched alkenyl radical and a linear or branched alkoxy radical        having from 1 to 3 carbon atoms;    -   Z represents a residue comprising sterically hindered        piperidinyl group(s) which is chosen from:        -   ♦ the residues of formula:            in which:    -   R¹ is a divalent hydrocarbonaceous radical chosen from:    -   linear or branched alkylene radicals having from 2 to 18 carbon        atoms;    -   alkylenecarbonyl radicals, the linear or branched alkylene part        of which comprises 2 to 20 carbon atoms;    -   alkylenecyclohexylene radicals, the linear or branched alkylene        part of which comprises from 2 to 12 carbon atoms and the        cyclohexylene part of which comprises an —OH group and        optionally 1 or 2 alkyl radicals having from 1 to 4 carbon        atoms;    -   radicals of formula —R⁴—O—R⁵— in which the R⁴ and R⁵ radicals,        which are identical or different, represent alkylene radicals        having 1 to 12 carbon atoms;    -   radicals of formula —R⁴—O—R⁵— in which the R⁴ and R⁵ radicals        have the meanings indicated above and one or both of them are        substituted by one or two OH group(s);    -   radicals of formulae —R⁴—COO—R⁵— and —R⁴—OCO—R⁵— in which R⁴ and        R⁵ have the above meanings; radicals of formula        —R⁶—O—R⁷—O—CO—R⁸— in which R⁶, R⁷ and R⁸, which are identical or        different, represent alkylene radicals having from 2 to 12        carbon atoms and the R⁷ radical is optionally substituted by a        hydroxyl group;    -   U represents —O— or —NR⁹—, R⁹ being a radical chosen from: a        hydrogen atom; a linear or branched alkyl radical having from 1        to 6 carbon atoms; a divalent radical —R¹— which has the meaning        indicated above, one of the valency bonds being connected to the        nitrogen atom of —NR⁹— and the other being connected to a        silicon atom; and a divalent radical of formula:    -    in which R¹ has the meaning indicated above, R² and R³ have the        meanings indicated below and R¹⁰ represents a linear or branched        alkylene radical having 1 to 12 carbon atoms, one of the valency        bonds (that of R¹⁰) being connected to the nitrogen atom of        —NR⁹— and the other (that of R¹) being connected to a silicon        atom;    -   R² are identical or different radicals chosen from linear or        branched alkyl radicals having from 1 to 3 carbon atoms and the        phenyl radical;    -   R³ represents a hydrogen atom or the R² radical;    -   ♦ and those of formula:        in which:    -   R′¹ is chosen from a trivalent radical of formula:    -    where m represents a number from 2 to 20,    -    and a trivalent radical of formula:    -    where n represents a number from 2 to 20;    -   U′ represents —O— or —NR¹¹—, R¹¹ being a hydrogen atom or a        linear or branched alkyl radical having from 1 to 6 carbon        atoms;    -   R² and R³ have the same meanings as those given with respect to        the formula (II);    -   a is a number chosen from 0, 1 and 2;    -   b is a number chosen from 0, 1 and 2;    -   the sum a+b is at most equal to 2.

This polyorganosiloxane (VIII) can additionally comprise at least oneother siloxyl unit of formula: $\begin{matrix}{(R)_{c}(X)_{d}{{V{Si}}(O)}_{\frac{3 - {({c + d})}}{2}}} & ({III})\end{matrix}$

-   -   in which:        -   the R and X symbols have the same meanings as those given            above with respect to the formula (I);        -   the V symbol represents: a linear or branched alkyl radical            having from 5 to 20 carbon atoms; a radical of formula            —(CH₂)_(p)—COO—R¹² in which p represents a number from 5 to            20 and R¹² represents a linear or branched alkyl radical            having from 1 to 12 carbon atoms; a radical of        -    formula —(CH₂)_(q)—O—R¹³ in which q represents a number            from 3 to 10 and R¹³ represents a hydrogen atom, an ethylene            oxide sequence, a propylene oxide sequence, a mixed ethylene            oxide+propylene oxide sequence or an acyl radical having            from 2 to 12 carbon atoms;    -   c is a number chosen from 0, 1 and 2;    -   d is a number chosen from 0, 1 and 2;    -   the sum c+d is at most equal to 2.

It can also advantageously comprise other siloxyl unit(s) of formula:$\begin{matrix}{(R)_{e}(X)_{f}{{Si}(O)}_{\frac{4 - {({e + f})}}{2}}} & ({IV})\end{matrix}$in which:

-   -   R and X have the same meanings as those given with respect to        the formula (I);    -   e is a number chosen from 0, 1, 2 and 3;    -   f is a number chosen from 0, 1, 2 and 3;    -   the sum e+f is at most equal to 3.

Thus, preferably, the polyorganosiloxane (VIII) is a linearpolydiorganosiloxane of mean formula:

in which:

-   -   the R, Z and V symbols have the meanings given above with        respect to the formulae (I) and (III);    -   the Y symbol represents a monovalent radical chosen from the R,        Z, V and X radicals;    -   the R¹⁴ symbols are identical or different and represent a        monovalent radical chosen from an R radical and an X radical as        defined above with respect to the formula (I);    -   r, s and t are equal to zero or represent integers or fractional        numbers of greater than zero, with the additional condition        according to which, if r=0, at least one of the two Y radicals        represents the Z radical.

According to a preferred embodiment, the compound comprising apiperidinyl functional group corresponds to the following formula:

-   -   in which        -   x″ is between 0 and 1000,        -   y″ is between 1 and 50,            the proportion of compound (VI) in the composition            preferably being between 0.2 and 5%.

The present compound, in the form of an oil, advantageously makes itpossible to obtain a composition for which the Bingham threshold canreach 350 Pa.

The polyorganosiloxane (I) is, by weight, one of the essentialconstituents of the composition used according to the invention.Advantageously, it is a product exhibiting units of formula:$\begin{matrix}{W_{a}Z_{b}^{\prime}{SiO}_{\frac{4 - {({a + b})}}{2}}} & ({VII})\end{matrix}$

-   -   in which:        -   W is an alkenyl group, preferably a vinyl or allyl group,        -   Z′ is a monovalent hydrocarbonaceous group which has no            unfavourable effect on the activity of the catalyst and is            preferably chosen from alkyl groups having from 1 to 8            carbon atoms inclusive, advantageously from the methyl,            ethyl, propyl and 3,3,3-trifluoropropyl groups, and as well            from aryl groups, advantageously from the xylyl, tolyl and            phenyl radicals,    -   a is 1 or 2, b is 0, 1 or 2, and a+b is between 1 and 3,        preferably between 2 and 3,        optionally at least a portion of the other units being units of        mean formula: $\begin{matrix}        {Z_{c}^{\prime}{SiO}_{\frac{4 - c}{2}}} & ({VIII})        \end{matrix}$        in which Z′ has the same meaning as above and c has a value of        between 0 and 3, preferably between 2 and 3.

It is advantageous for this polydiorgano-siloxane to have a viscosity atleast equal to 100 mPa·s, preferably to 500 mPa·s, and more preferablystill of between 500 and 100 000 mPa·s. Mention may be made, by way ofexample of compound (I), of poly-dimethylsiloxane.

The polydimethylsiloxane (I) can be formed solely of units of formula(VII) or can additionally comprise units of formula (VIII). Likewise, itcan exhibit a linear, branched, cyclic or network structure. Its degreeof polymerization is preferably between 2 and 5000.

Z′ is generally chosen from the methyl, ethyl and phenyl radicals, atleast 60 mol % of the Z′ radicals being methyl radicals.

Examples of siloxyl units of formula (VII) are the vinyldimethylsiloxaneunit, the vinylphenyl-methylsiloxane unit and the vinylsiloxane unit.

Examples of siloxyl units of formula (VIII) are the SiO_(4/2),dimethylsiloxane, methylphenylsiloxane, diphenylsiloxane, methylsiloxaneand phenylsiloxane units.

Examples of polyorganosiloxanes (I) are dimethylpolysiloxanes comprisingdimethylvinylsilyl ends, methylvinyldimethylpolysiloxane copolymerscomprising trimethylsilyl ends, methylvinyldimethylpolysiloxanecopolymers comprising dimethylvinylsilyl ends, or cyclicmethylvinylpolysiloxanes.

The polyorganosiloxane (II) is preferably of the type of thosecomprising siloxyl units of formula: $\begin{matrix}{H_{d}L_{e}{SiO}_{\frac{4 - {({d + e})}}{2}}} & ({IX})\end{matrix}$in which:

-   -   L is a monovalent hydrocarbonaceous group which has no        unfavourable effect on the activity of the catalyst and which is        preferably chosen from alkyl groups having from 1 to 8 carbon        atoms inclusive, advantageously from the methyl, ethyl, propyl        and 3,3,3-trifluoropropyl groups, and as well from aryl groups,        advantageously from the xylyl, tolyl and phenyl radicals,    -   d is 1 or 2, e is 0, 1 or 2, and d+e has a value of between 1        and 3,    -   optionally, at least a portion of the other units being units of        mean formula: $\begin{matrix}        {L_{g}{SiO}_{\frac{4 - g}{2}}} & (X)        \end{matrix}$        in which L has the same meaning as above and g has a value of        between 0 and 3, preferably between 2 and 3.

The dynamic viscosity of this polyorganosiloxane is at least equal to 5,preferably to 10, and more preferably still is between 20 and 1000mPa·s. The dynamic viscosity, referred to as “newtonian”, is the dynamicviscosity which is measured at 25° C., in a way known per se, at a shearrate gradient which is sufficiently low for the viscosity measured to beindependent of the rate gradient.

Mention may be made, as examples of polyorganosiloxane (II), ofpoly(dimethylsiloxane)(methylhydrosiloxy)-α,ω-dimethylhydrosiloxane.

The polyorganosiloxane (II) can be formed solely of units of formula(IX) or additionally comprises units of formula (X).

The polyorganosiloxane (II) can exhibit a linear, branched, cyclic ornetwork structure. The degree of polymerization is greater than or equalto 2. More generally, it is less than 5000.

The L group has the same meaning as the Z group above.

Examples of units of formula (IX) are:H(CH₃)₂SiO_(1/2), HCH₃SiO_(2/2), H(C₆H₅)SiO_(2/2)

The examples of units of formula (X) are the same as those given abovefor the units of formula (VIII).

Examples of polyorganosiloxane (II) are:

-   -   dimethylpolysiloxanes comprising        -   hydrodimethylsilyl ends,    -   copolymers comprising        -   (dimethyl)hydromethylpolysiloxane (dimethyl) units            comprising trimethylsilyl ends,    -   copolymers comprising        -   (dimethyl)hydromethylpolysiloxane units comprising            hydrodimethylsilyl ends,    -   hydromethylpolysiloxanes comprising        -   trimethylsilyl ends,    -   cyclic hydromethylpolysiloxanes.

The ratio of the number of hydrogen atoms bonded to the silicon in thepolyorganosiloxane (I) to the number of groups comprising alkenylunsaturation of the polyorganosiloxane (II) is between 0.4 and 10,preferably between 0.6 and 5.

The polyorganosiloxane (I) and/or the polyorganosiloxane (II) can bediluted in a nontoxic organic solvent compatible with silicones.

The network polyorganosiloxanes (I) and (II) are commonly known assilicone resins.

The bases for polyaddition silicone compositions may comprise onlylinear polyorganosiloxanes (I) and (II), such as, for example, thosedisclosed in Patents: U.S. Pat. No. 3,220,972, U.S. Pat. No. 3,697,473and U.S. Pat. No. 4,340,709, or may simultaneously comprise branched ornetwork polyorganosiloxanes (I) and (II), such as, for example, thosedisclosed in Patents: U.S. Pat. No. 3,284,406 and U.S. Pat. No.3,434,366.

According to a specific embodiment, the following are employed:

-   -   at least one linear polyorganosiloxane (I) comprising chains        formed of units of formula (VIII) where c=2, blocked at each of        their ends by units of formula (VII) where a=1 and b=2, and    -   at least one linear polyorganosiloxane (II) comprising, in its        structure, at least three hydrogen atoms bonded to the silicon        which are situated in the chains and/or at the chain ends;    -   and more preferably still,    -   at least one linear polyorganosiloxane (I) comprising chains        formed of units of formula (VIII) where c=2, blocked at each of        their ends by units of formula (VII) where a=1 and b=2, and    -   at least one linear polyorganosiloxane (II) comprising chains        formed of units of formula (IX) where d=1 and e=1 and optionally        of units of formula (X) where g=2, blocked at each of their ends        by units of formula (IX) where d=1 and e=2.

The catalysts (III) are also well known. Use is preferably made ofplatinum and rhodium compounds. Use may in particular be made of thecomplexes of platinum and of an organic product disclosed in U.S. Pat.No. 3,159,601, U.S. Pat. No. 3,159,602 and U.S. Pat. No. 3,220,972 andEuropean Patents EP-A-0 057 459, EP-A-0 188 978 and EP-A-0 190 530, ofthe complexes of platinum and of vinylated organosiloxanes disclosed inU.S. Pat. No. 3,419,593, U.S. Pat. No. 3,715,334, U.S. Pat. No.3,377,432 and U.S. Pat. No. 3,814,730. The catalyst generally preferredis platinum. In this case, the amount by weight of catalyst (III),calculated as weight of platinum metal, is generally between 2 and 400ppm, preferably between 5 amd 200 ppm, based on the total weight of thepolyorganosiloxanes (I) and (II).

In accordance with a provision of the invention, the composition can beused for adhesive bonding. In the context of this application, it ispossible and even recommended to add an adhesion promoter (IV) to thecomposition.

On the other hand, when the composition is used for moulding, thecomposition does not comprise an adhesion promoter.

The promoter (IV), when it is used, comprises:

-   -   (IV.1) at least one alkoxylated organosiloxane comprising, per        molecule, at least one C₂-C₆ alkenyl group,    -   (IV.2) at least one organosilicon compound comprising at least        one epoxy radical,    -   (IV.3) at least one metal M chelate and/or one metal alkoxide of        general formula:    -    M(OJ)_(n), with n=valency of M and    -    J=linear or branched C₂-C₆ alkyl.

Advantageously, the alkoxylated organosiloxane (IV.1) corresponds to thefollowing general formula:

in which:

-   -   R″¹, R′² and R′³ are hydrogen or hydrocarbonaceous radicals        which are identical to or different from one another and        preferably represent hydrogen, a linear or branched C₁-C₄ alkyl        or a phenyl optionally substituted by at least one C₁-C₃ alkyl,    -   A is a linear or branched C₁-C₄ alkylene or a divalent group of        formula —CO—O-alkylene_(▪), where the alkylene residue is as        defined above and the valency _(▪) is bonded to the Si via G,    -   L is a valency bond or oxygen,    -   R′⁴ and R′⁵ are identical or different radicals and represent a        linear or branched C₁-C₄ alkyl,    -   x′=0 or 1,    -   x=0 to 4, preferably 0 or 1 and more preferably still 0.

Without this being limiting, it may be considered thatvinyltrimethoxysilane is a particularly appropriate compound (IV.1).

The organosilicon compound (IV.2) of the promoter (IV) is chosen:

-   -   either from the products (IV.2a) of following general formula:    -   in which:    -   R′⁶ is a linear or branched C₁-C₄ alkyl radical,    -   R′⁷ is a linear or branched alkyl radical,    -   y is equal to 0, 1, 2 or 3, preferably to 0 or 1 and more        preferably still to 0,    -   X′ is equal to:    -   with        -   E and D being identical or different radicals chosen from            linear or branched C₁-C₄ alkylenes,        -   z being equal to 0 or 1,        -   R′⁸, R′⁹ and R′¹⁰ being identical or different radicals            representing hydrogen or a linear or branched C₁-C₄ alkyl,            hydrogen being more particularly preferred,        -   it being possible for R′⁸, R′⁹ and R′¹⁰ alternatively to            constitute, together with the two carbons carrying the            epoxy, an alkyl ring having from 5 to 7 ring members,    -   or from the products (IV.2b) composed of epoxyfunctional        polydiorganosiloxanes comprising at least one unit of formula:        $\begin{matrix}        {X_{p}^{\prime}G_{q}{SiO}_{\frac{4 - {({p - q})}}{2}}} & ({XIII})        \end{matrix}$    -   in which:        -   X′ is the radical as defined above for the formula (XII),        -   G is a monovalent hydrocarbonaceous group which has no            unfavourable effect on the activity of the catalyst and            which is preferably chosen from alkyl groups having from 1            to 8 carbon atoms inclusive, advantageously from the methyl,            ethyl, propyl and 3,3,3-trifluoropropyl groups, and as well            from aryl groups, advantageously from the xylyl, tolyl and            phenyl radicals,        -   p=0, 1 or 2,        -   q=1, 2 or 3,        -   p+q=0, 1, 2 or 3,        -   optionally at least a portion of the other units of these            polydiorganosiloxanes being units of mean formula:            $\begin{matrix}            {G_{r}{SiO}_{\frac{4 - r}{2}}} & ({XIV})            \end{matrix}$        -    in which G has the same meaning as above and r has a value            of between 0 and 3, for example between 1 and 3.

The compounds (IV.2) are thus preferably epoxyalkoxysililcon compoundsand more preferably still epoxyalkoxymonosilanes (IV.2a).

Mention may be made, as examples of such compounds (IV.2), of:

-   -   -3-glycidoxypropyltrimethoxysilane (GLYMO)    -   or 3,4-epoxycyclohexylethyltrimethoxysilane.

As regards the final essential compound (IV.3) of the adhesion promoter(IV), the preferred products are those in which the metal M of thechelate and/or of the alkoxide (IV.3) is chosen from the following list:Ti, Zr, Ge, Li and Mn. It should be emphasized that titanium is moreparticularly preferred. An alkyl radical of butyl type, for example, canbe combined with it.

In practice, the adhesion promoter (IV) is, for example:

-   -   vinyltrimethoxysilane (VTMO)(IV.1),    -   3-glycidoxypropyltrimethoxysilane (GLYMO)(IV.2),    -   and butyl titanate (IV.3).

Quantitatively, it may be specified that the proportions by weightbetween (IV.1), (IV.2) and (IV.3), when an adhesion promoter is used,expressed as percentages by weight with respect to the total of thethree, are as follows:

-   -   (IV.1) of between 15 and 70 and preferably between 30 and 50,    -   (IV.2) of between 15 and 70 and preferably between 30 and 50,    -   (IV.3) of between 5 and 25 and preferably between 10 and 20,        it being understood that the sum of these proportions of (IV.1),        (IV.2) and (IV.3) is equal to 100%.

The filler (V) employed is composed of products chosen from siliceous(or nonsiliceous) materials.

As regards the siliceous materials, they can act as reinforcing orsemi-reinforcing filler.

The reinforcing siliceous fillers are chosen from colloidal silicas,fumed and precipitated silica powders, or their mixtures.

These powders exhibit a mean particle size generally of less than 0.1 μmand a BET specific surface of greater than 50 m²/g, preferably ofbetween 100 and 350 m²/g.

Semi-reinforcing siliceous fillers, such as diatomaceous earths orground quartz, can also be employed.

As regards the nonsiliceous inorganic materials, they can be involved assemi-reinforcing or bulking inorganic filler. Examples of thesenonsiliceous fillers, which can be used alone or as a mixture, arecarbon black, titanium dioxide, aluminium oxide, alumina hydrate,expanded vermiculite, nonexpanded vermiculite, calcium carbonate, zincoxide, mica, talc, zirconates, iron oxide, barium sulphate and slakedlime. These fillers have a particle size generally of between 0.001 and300 μm and a BET specific surface of less than 100 m²/g.

In practice but without implied limitation, the filler employed isquartz or a mixture of quartz and silica.

The filler can be treated by all or part of at least one and/or other ofthe compounds (IV.1) to (IV.3) of the promoter (IV).

In the case in particular of the use of a particulate siliceousinorganic filler, the filler can advantageously be employed in the formof the suspension obtained by treating the filler Dv application of themethod in accordance with the teaching of Patent ApplicationWO-A-98/58997, which provides a two-step treatment of the filler by acompatibilizing agent (chosen for example: as regards the firsttreatment step, from a silazane, a hydroxylated siloxane, an amine or anorganic acid; and, as regards the second treatment step, from asilazane), the treatment being carried out in the presence of the POS(I) constituent. In the case where such treatment results in a basic pH,a neutralizing agent, such as, for example, a weak acid or a silicafiller, such as ground quartz, can be added to the dispersion.

As far as the weight is concerned, it is preferable to employ an amountof filler of between 20 and 50%, preferably between 25 and 35%, byweight with respect to the combined constituents of the composition.

Advantageously, the silicone elastomer composition comprises at leastone retardant (VI) of the addition reaction (crosslinking inhibitor)chosen from the following compounds:

-   -   polyorganosiloxanes which are advantageously cyclic and        substituted by at least one alkenyl,        tetramethylvinyltetrasiloxane being particularly preferred,    -   pyridine,    -   organic phosphites and phosphines,    -   unsaturated amides,    -   alkyl maleates    -   and acetylenic alcohols.

These acetylenic alcohols (cf. FR-B-1 528 464 and FR-A-2 372 874), whichare among the preferred thermal blockers of the hydrosilylationreaction, have the formula:R¹⁵—(R¹⁶)C(OH)C≡CHin which formula:

-   -   R¹⁵ is a linear or branched alkyl radical or a phenyl radical;    -   R¹⁶ is H, a linear or branched alkyl radical or a phenyl        radical;        it being possible for the R¹⁵ and R¹⁶ radicals and the carbon        atom situated a to the triple bond optionally to form a ring;        the total number of carbon atoms present in R¹⁵ and R¹⁶ being at        least 5, preferably from 9 to 20.

The said alcohols are preferably chosen from those exhibiting a boilingpoint of greater than 250° C. Mention may be made, by way of examples,of:

-   -   1-ethynyl-1-cyclohexanol;    -   3-methyldodec-1-yn-3-ol;    -   3,7,11-trimethyldodec-1-yn-3-ol;    -   1,1-diphenylprop-2-yn-1-ol;    -   3-ethyl-6-ethylnon-1-yn-3-ol;    -   3-methylpentadec-1-yn-3-ol.

These α-acetylenic alcohols are commercial products.

Such a retardant (VI) is present in a proportion of at most 3000 ppm,preferably in a proportion of 100 to 2000 ppm, with respect to the totalweight of the organopolysiloxanes (I) and (II).

The composition used according to the invention can comprise at leastone unsaturated POS resin (VII) comprising at least two alkenylresidues, preferably vinyl residues, per molecule.

Advantageously, the POS resin (VII) comprises, in its structure, from0.1 to 20% by weight of alkenyl group(s), the said structure exhibitingat least two different units chosen from units of M, D, T and Q types,at least one of these units being a unit of T or Q type.

In practice, this resin (VII) preferably corresponds to one of the threefollowing formulae:MM^(Vi)DD^(Vi)Q  (XV)orMD^(Vi)Q  (XVI)orMM^(Vi)Q (XVII)

This resin (VII) participates in the establishment of the rheological,mechanical and adhesive properties of the composition. It is known thatthe Q siloxyl units play a relatively important role in this respect.Thus, in accordance with an advantageous provision of the invention, theresin (VII) comprises Q units in a proportion of at least 5% preferablyat least 7%, and more preferably still in a proportion of 8 to 30%.

According to an alternative form, the resin (VII) comprises T siloxylunits.

In a way known per se, the silicone elastomer composition can have addedto it various conventional additives, such as, for example, colorants.

More advantageously still, the composition according to the inventioncomprises at least one reinforcing filler, such as a silicic filler, ora paste.

According to a particularly preferred embodiment, the composition usedaccording to the invention involves the constituents (I) to (VIII) inthe following proportions, as % by weight on a dry basis with respect tothe total weight: (I)  1 to 80 preferably 10 to 60 (II) 0.1 to 20 preferably 0.5 to 10  (III) 0.0002 to 0.04  preferably 0.0005 to 0.02 (IV.1) 0.01 to 5   preferably 0.05 to 2   (IV.2) 0.01 to 5   preferably0.05 to 2   (IV.3) 0.01 to 3   preferably 0.1 to 1   (V)  0 to 90preferably 10 to 80 (VI)   0 to 0.5 preferably 0.005 to 0.3  (VII)  0 to80 preferably  5 to 70 (VIII) 0.2 to 5   preferably 0.5 to 2. 

According to another of its aspects, the present invention relates to atwo-component precursor system of the silicone elastomer compositiondescribed above.

Such a precursor system is provided in two separate parts A and Bintended to be mixed to form the composition, one of these parts A or Bcomprising the catalyst (III) and a single polyorganosiloxane entity (I)or (II). Another characteristic of this precursor system is that itspart A or B comprising the compound (IV.1) of the promoter (IV) does notcomprise the catalyst (III), that the resin (VII) can be employed in thepart A or the part B or in both parts A and B, the part A or Bcomprising the POS (II) and the resin (VII) being devoid of catalyst(III), and, finally, that the thixotropic compound (VIII) can beemployed in the part A or B comprising the catalyst (III).

The viscosity of the parts A and B and of their mixture can be adjustedby varying the amounts of the constituents and by choosingpolyorganosiloxanes of different viscosities.

Once mixed with one another, the parts A and B form a ready-for-usesilicone elastomer composition which can be applied to the substrates tobe adhesively bonded or to be coated by an appropriate means (forexample, doctor blade, nozzle, gun, brush, screen printing, and thelike).

The composition applied to the support to be coated can be crosslinkedthermally and/or by infrared radiation.

According to a noteworthy characteristic of the use according to theinvention, the substrates which can be adhesively bonded by thecomposition are made of thermoplastic or thermosetting polymer,preferably of phenoplast, of polyamide, of polyester, of ABS, ofpolycarbonate, of PVC, of polyether, of polyolefin or of epoxy resin.

The substrates can also be metal substrates. They can, e.g., be: raw ortreated aluminiums, raw or treated steels, or enamelled metals.

Thus it is that the composition according to the invention isself-adhesive on aluminium (type AG3) and on steel (type Sollac R 1426)with a shear strength of 1 to 5 MPa and 100% cohesive failure in allcases.

The field of application of the use recommended by the invention isadvantageously that of the adhesive bonding of components for theconstruction of vehicles, in particular motor vehicles, or that of theadhesive bonding of components for the construction of domesticelectrical appliances, in particular electric irons.

In practice, the adhesive bonding applications in the automobileindustry can be:

-   -   flexible adhesive bonding of plastic and metal components under        the engine bonnet and in the passenger compartment,    -   adhesive bonding of headlamp units.

According to an alternative form, this field of application can also bethat of the adhesive bonding of electrical/electronic components, inparticular in the domestic electrical appliance industry.

According to another alternative form, the field of application can alsobe that of the moulding of forms to be reproduced. This is because thelow dripping of the composition according to the invention confersthereon a very particular advantage for its application with regard tocomponents or substrates to be reproduced and thus which have to bemoulded.

The examples which follow describe the preparation of the crosslinkablesilicone composition according to the invention. These examples willallow its advantages to emerge. They refer to the drawings, in which:

FIG. 1 represents the curve of the change in the viscosity and in theBingham threshold of a composition, the part A of the two-componentsystem, comprising 2.5% of 200 m²/g silica pretreated and additivatedwith a POS oil comprising a piperidinyl functional group,

FIG. 2 represents the curve of the change in the viscosity and in theBingham threshold of a composition, the part A of the two-componentsystem, comprising 10% of a dispersion of silica treated in situ andadditivated with a POS oil comprising a piperidinyl functional group.

EXAMPLES Example 1 Formulation of the Parts A and B of a Two-ComponentCrosslinkable Silicone Composition

Part A of the Two-Component System

The following are mixed in a reactor at ambient temperature:

-   -   41.6 parts by weight of a resin of type (VII) MM^(Vi)DD^(Vi)Q        comprising 0.9% by weight of vinyl (Vi) groups and composed of        21% by weight of (CH₃)₃SiO_(0.5) units, 0.2% by weight of        (CH₃)₂ViSiO_(0.5) units, 67.8% by weight of (CH₃)₂SiO units, 3%        by weight of (CH₃)ViSiO units and 8% by weight of SiO₂ units    -   24.8 parts by weight of a PDMS oil (I), blocked by        (CH₃)₂ViSiO_(0.5) units, having a viscosity of 100 000 mPa·s and        comprising 0.005 SiVi functional group per 100 g of oil    -   32.9 parts by weight of inorganic filler (V), in the form of        ground quartz with a mean particle size of approximately 2 μm    -   0.7 part by weight of tetrabutyl orthotitanate (TBOT) (IV.3)    -   0.004 part by weight of platinum (III) metal in the form of a        metal complex known under the name of Karstedt catalyst.        Part B of the Two-Component System

The following are mixed in a reactor at ambient temperature:

-   -   26.8 parts by weight of a resin (VII) with the structure        MM^(Vi)DD^(Vi)Q comprising 0.9% by weight of vinyl (Vi) groups        and composed of 21% by weight of (CH₃)₃SiO_(0.5) units, 0.2% by        weight of (CH₃)₂ViSiO_(0.5) units, 67.8% by weight of (CH₃)₂SiO        units, 3% by weight of (CH₃)ViSiO units and 8% by weight of SiO₂        units    -   14.1 parts by weight of PDMS oil (I), blocked by        (CH₃)₂ViSiO_(0.5) units, having a viscosity of 100 000 mPa·s and        comprising 0.005 SiVi functional group per 100 g of oil    -   49 parts by weight of inorganic filler (V), in the form of        ground quartz, with a mean particle size of approximately 2 μm    -   2.5 parts by weight of 200 m²/g silica pretreated with a cyclic        POS    -   3.9 parts by weight of a poly(dimethyl)(hydromethyl)siloxane        (II), blocked by (CH₃)₂HSiO_(0.5) units, having a viscosity of        25 mPa·s and comprising, in total, 0.7 SiH functional group per        100 g of oil    -   0.05 part by weight of ethynylcyclohexanol (VI)    -   1.8 parts by weight of vinyltrimethoxysilane (VTMO) (IV.1)    -   1.8 parts by weight of γ-glycidoxypropyltrimethoxysilane (GLYMO)        (IV.2)    -   0.1 part by weight of black colouring base.

The two-component system is obtained by mixing 100 parts of A and 100parts of B at ambient temperature.

Example 2 Rheological and Mechanical Properties of the Part A of theTwo-Component System Additivated with a POS Oil Comprising a PiperidinylFunctional Group (VIII)

For the laboratory evaluations, the product is employed from acompressed-air spray gun which makes it possible to extrude the productpresent in two-component cartridges (2×200 cc): the mixing is carriedout using a static mixer placed immediately at the outlet of thecartridge.

The rheological and mechanical properties are evaluated by additivationof the part A of the two-component system with a POS oil comprising apiperidinyl functional group (VIII). The part B remains identical. ThePOS comprising a piperidinyl functional group is of formula:

in the form of an oil with a viscosity of approximately 10 000 mPa·scomprising 0.25% by weight of nitrogen. This oil is added to the part Aof the two-component system at 0.5 (Test 1), 1 (Test 2) and 2% (Test 3).The mixture is homogenized by hand using a spatula. The rheological andmechanical performances of the composition thus obtained are measured inthe following way:

-   -   the Theological properties were measured on a CarriMed rheometer        with a cone of diameter 2.0 cm and an angle of 1°.    -   the yield point is determined by the computer of the device by        applying a Bingham fluid model.    -   the mechanical properties were measured on H2 test specimens. To        do this, a film with a thickness of 2 mm is produced: the        product is crosslinked at 150° C. for 1 hour under a heating        press. The test specimens are subsequently removed, a shore A        hardness measurement is carried out and then the mechanical        properties (tensile strength, modulus, elongation) are evaluated        using a dynamometer of Zwick type with a pull rate of 500        mm/min.

The results of these tests are combined in Table 1 below: TABLE 1 Test 1Test 2 Test 3 Control 0.5% 1% 2% Viscosity (Pa · s) 100 000 102 000 104000 100 000 Bingham threshold (PA) 45 85 118 132 Tensile strength 5.6 54.9 5 T/S (MPa) Elongation at break 264 239 246 271 E/B (%) 100% Modulus(MPa) 2.1 2.2 2.1 2 Shore hardness A 3 × 2 mm 44.1 44.7 46.5 41.5

These results show that the addition of the POS oil comprising apiperidinyl functional group has an effect on the Theological propertiesof the part A of the two-component system. Specifically, the greater thecontent of oil, the greater the yield point. On the other hand, it isfound that the addition of oil does not have any significant effect onthe viscosity of the composition A or on the mechanical properties ofthe two-component system.

Example 3 Rheological and Mechanical Properties of the Part A of theTwo-Component System Comprising 2.5% of 200 m²/g Silica Pretreated andAdditivated with a POS Comprising a Piperidinyl Functional Group asThixotropic Additive

The preceding example is repeated, except that 2.5% of pretreated 200m²/g silica are added to the particle A as reinforcing filler.

The results of the tests are combined in Table 2 below: TABLE 2 Test 4Test 5 Test 6 Control 0.5% 1% 2% Viscosity (Pa · s) 75 000 80 000 75 00082 000 Bingham threshold (PA) 75 165 250 320 Tensile strength 5.9 5.95.8 5.2 T/S (MPa) Elongation at break 243 232 260 251 E/B (%) 100%Modulus (MPa) 2.9 2.9 2.5 2.3 Shore hardness A 3 × 2 mm 49.7 50 47.548.1

The results show that, in the presence of silica in the composition ofthe part A, the effect of the POS oil comprising a piperidinylfunctional group (VIII) on the yield point is reinforced with respect tothe action of the same oil on a silica-free composition as presented inExample 2. In the same way as in Example 2, the viscosity of thecomposition and the mechanical properties of the two-component systemare not significantly modified by the addition of the oil.

Example 4 Rheological and Mechanical Properties of the Part A of theTwo-Component System Comprising Various Levels of Dispersion of SilicaTreated In Situ and Additivated with a POS Comprising a PiperidinylFunctional Group

Example 2 is repeated, except that different parts A, each comprising adifferent level of reinforcing filler contributed by the dispersion ofsilica, are prepared. The POS oil comprising a piperidinyl functionalgroup as defined in Example 2 is added to each of these compositions atlevels of 0.5, 1 and 2%.

The dispersion of silica treated in situ is obtained in the followingway: The following are introduced into a Z-arm laboratory mixer:

-   -   74 parts of (CH₃)ViSiO_(0.5)-terminated PDMS with a viscosity of        600 mPa·s,    -   2 parts of water,    -   30 parts of silica with an expanded surface of 200 m²/g.        After incorporation, 5 parts of hexamethyldisilazine are added.        Mixing is continued for 1 hour, before heating the reactor in        order to gradually remove the volatile compounds.

The results obtained with a part A comprising 10% of dispersion ofsilica treated in situ are combined in Table 3: TABLE 3 Test 7 Test 8Test 9 Control 0.5% 1% 2% Viscosity (Pa · s) 80 000 82 000 81 000 83 000Bingham threshold (PA) 51 125 155 165 Tensile strength 6.5 6 5.6 5.6 T/S(MPa) Elongation at break 200 222 212 196 E/B (%) 100% Modulus (MPa)3.28 2.8 2.7 3 Shore hardness A 3 × 2 mm 46.5 50.3 48 49.5

The results obtained with a part A comprising 15% of dispersion ofsilica treated in situ are combined in Table 4: TABLE 4 Test 10 Test 11Test 12 Control 0.5% 1% 2% Viscosity (Pa · s) 84 000 91 000 80 000 81000 Bingham threshold (PA) 65 148 210 250 Tensile strength 6.7 6.2 6.15.4 T/S (MPa) Elongation at break 176 204 198 217 E/B (%) 100% Modulus(MPa) 4 3 3.2 2.4 Shore hardness A 3 × 2 mm 49.7 52 51.5 47.3

The results obtained with a part A comprising 20% of dispersion ofsilica treated in situ are combined in Table 5: TABLE 5 Test 13 Test 14Test 15 Control 0.5% 1% 2% Viscosity (Pa · s) 112 000 104 000 106 000107 000 Bingham threshold (PA) 100 225 300 350 Tensile strength 6.7 6.16.1 5.6 T/S (MPa) Elongation at break 192 191 156 166 E/B (%) 100%Modulus (MPa) 3.5 3.3 4.2 3.9 Shore hardness A 3 × 2 mm 53.5 52.5 56.755.5

The results in Table 3 show that, in the presence of dispersion ofsilica treated in situ in the part A of the two-component system, theeffect of the POS oil comprising a piperidinyl functional group (VIII)on the yield point is reinforced with respect to the action of the sameoil on a composition without silica dispersion as presented in Example2.

Comparison of the results in Tables 3, 4 and 5 shows that the yieldpoint increases in proportion as the level of silica dispersion in thepart A of the two-component system increases.

The mechanical properties and the viscosity of the two-component systemwith various levels of paste formation are not modified with theaddition of the POS oil comprising a piperidinyl functional group.

Example 5 Study of the Change Over Time in the Rheological Properties ofthe Part A of the Two-Component System Comprising 2.5% of Pretreated 200m²/g Silica and Additivated with a POD Comprising a PiperidinylFunctional Group

The various compositions described in Example 2 have formed the subjectof a measurement of viscosity and of Bingham threshold after storage for0, 2, 7, 21, 50, 80 and 120 days, in order to study the change over timein the rheological properties of the additivated compositions withrespect to the control composition and thus to determine the effects ofthe POS oil comprising a piperidinyl functional group after storage.

This change is represented in the form of curves in FIG. 1. In thisfigure, the solid curves are the viscosity curves while the dottedcurves are those of the Bingham threshold. The key to the varioussymbols is as follows:

-   -   ▪ control (part A comprising 2.5% of pretreated 200 m²/g silica)    -   ♦ part A comprising 2.5% of pretreated 200 m²/g silica and 0.5%        of POS oil comprising a piperidinyl functional group    -   ● part A comprising 2.5% of pretreated 200 m²/g silica and 1% of        POS oil comprising a piperidinyl functional group    -   part A comprising 2.5% of pretreated 200 m²/g silica and 2% of        POS oil comprising a piperidinyl functional group.

It is found that the change over time of the various additivated parts Ais entirely equivalent to that of the nonadditivated control part A. ThePOS oil comprising a piperidinyl functional group therefore has noeffect over time on the part A of the two-component system whichcomprises pretreated 200 m²/g silica as additive. The part A of thetwo-component system according to the invention thus exhibitsrheological properties which are stable over time.

Example 6 Study of the Change Over Time in the Rheological Properties ofthe Part A of the Two-Component System Comprising 10% of Dispersion ofSilica Treated In Situ and Additivated with a POD Comprising aPiperidinyl Functional Group

Example 5 is repeated, except that the parts A are equivalent to thosetested in Example 4 and comprise only a single level of silicadispersion at 10%.

The change over time in the rheological properties of the variouscompositions is represented in FIG. 2. In this figure, the solid curvesare the viscosity curves while the dotted curves are those of theBingham threshold. The key to the various symbols is as follows:

-   -   ▪ control (part A comprising 10% of dispersion of silica treated        in situ)    -   ♦ part A comprising 10% of dispersion of silica treated in situ        and 0.5% of POS oil comprising a piperidinyl functional group    -   part A comprising 10% of dispersion of silica treated in situ        and 1% of POS oil comprising a piperidinyl functional group    -   ● part A comprising 10% of dispersion of silica treated in situ        and 2% of POS oil comprising a piperidinyl functional group.

As in Example 5, it is found that the change over time of the variousadditivated parts A is entirely equivalent to that of the nonadditivatedcontrol part A. The POS oil comprising a piperidinyl functional grouptherefore has no effect over time on the part A of the two-componentsystem which comprises the dispersion of silica treated in situ asadditive.

The examples presented show that the composition developed by theApplicant exhibits improved Theological properties, while retaining aviscosity which makes it possible for it to be easily handled, andfirst-rate mechanical properties. The use of reinforcing fillerssignificantly improves the rheological properties since the value of theyield point is multiplied by 4, this being achieved without modifyingthe viscosity or the mechanical properties. Finally, the compositionaccording to the invention, and in particular the part A constitutingit, has very good stability over time.

1-20. (Canceled)
 21. A crosslinkable adhesive silicone compositioncomprising: (I) at least one polyorganosiloxane exhibiting, permolecule, at least two alkenyl groups bonded to the silicon, (II) atleast one polyorganosiloxane exhibiting, per molecule, at least threehydrogen atoms bonded to the silicon, (III) a catalytically effectiveamount of at least one catalyst composed of at least one metal belongingto the platinum group, (IV) optionally, an adhesion promoter, (V) areinforcing or non-reinforcing inorganic filler, (VI) optionally, atleast one crosslinking inhibitor, (VII) optionally, at least onepolyorganosiloxane resin carrying Q and/or T siloxyl units and alkenylgroups, and (VIII) at least one compound comprising a cyclic aminefunctional group carried on a siloxane chain, as thixotropic additivewhich modifies the rheological properties of the composition byconferring thereon a high yield point.
 22. The composition according toclaim 21, wherein the cyclic amine functional group of the compound(VIII) is a piperidinyl functional group.
 23. The composition accordingto claim 21, wherein the compound (VIII) is a polyorganosiloxane having,per mole, at least one unit of general formula: $\begin{matrix}{(R)_{a}(X)_{b}Z\quad{Si}\quad(O)_{\frac{3 - {({a + b})}}{2}}} & (I)\end{matrix}$ wherein: the R symbols are identical or different andrepresent a monovalent hydrocarbon radical selected from the groupconsisting of a linear or branched alkyl radical having from 1 to 4carbon atoms, a phenyl radical and a 3,3,3-trifluoropropyl radical; theX symbols are identical or different and represent a monovalent radicalselected from the group consisting of a hydroxyl group, an alkenylradical and an alkoxy radical having from 1 to 3 carbon atoms; Zrepresents a group having sterically hindered piperidinyl group(s)selected from the group consisting of: a) groups of formula:

wherein: R¹ is a linear or branched alkylene radical having from 2 to 18carbon atoms; an alkylenecarbonyl radical whose linear or branchedalkylene part has 2 to 20 carbon atoms; an alkylenecyclohexyleneradical, whose linear or branched alkylene part has from 2 to 12 carbonatoms and the cyclohexylene part has an —OH group and, optionally, 1 or2 alkyl radicals having from 1 to 4 carbon atoms; a radical of formula—R⁴—O—R⁵— wherein the R⁴ and R⁵ radicals, identical or different,represent alkylene radicals having 1 to 12 carbon atoms; a radical offormula —R⁴—O—R⁵— wherein the R⁴ and R⁵ radicals have the meaningsindicated above and one or both of them are substituted by one or two OHgroup(s); a radical of formulae —R⁴—COO—R⁵— and —R⁴—OCO—R⁵— wherein R⁴and R⁵ have the above meanings; or a radical of formula—R⁶—O—R⁷—O—CO—R⁸— wherein R⁶, R⁷ and R⁸, identical or different,represent alkylene radicals having from 2 to 12 carbon atoms and the R⁷radical is optionally substituted by a hydroxyl group; U represents —O—or —NR⁹—, R⁹ being a hydrogen atom; a linear or branched alkyl radicalhaving from 1 to 6 carbon atoms; a divalent radical —R¹— which has themeaning indicated above, one of the valency bonds being connected to thenitrogen atom of —NR⁹— and the other being connected to a silicon atom;or a divalent radical of formula:

wherein R¹ has the meaning indicated above, R² and R³ have the meaningsindicated below and R¹⁰ represents a linear or branched alkylene radicalhaving 1 to 12 carbon atoms, one of the valency bonds (that of R¹⁰)being connected to the nitrogen atom of —NR⁹— and the other (that of R¹)being connected to a silicon atom; R² identical or different are fromlinear or branched alkyl radicals having from 1 to 3 carbon atoms or aphenyl radical; R³ represents a hydrogen atom or the R² radical; and b)groups of formula:

wherein: R′¹ is a trivalent radical of formula:

 wherein m represents a number from 2 to 20, Or a trivalent radical offormula:

 wherein n represents a number from 2 to 20; U′ represents —O— or —NR¹¹,R¹¹ being a hydrogen atom or a linear or branched alkyl radical havingfrom 1 to 6 carbon atoms; R² and R³ have the same meanings as thosegiven with respect to the formula (II); a is a number chosen from 0, 1and 2; b is a number chosen from 0, 1 and 2; and a+b is at most equal to2.
 24. The composition according to claim 23, wherein thepolyorganosiloxane (VIII) further comprises at least one other siloxylunit of formula: $\begin{matrix}{(R)_{c}(X)_{d}{{V{Si}}(O)}_{\frac{3 - {({c + d})}}{2}}} & ({III})\end{matrix}$ wherein: the R and X symbols have the same meanings asthose given above with respect to the formula (I); the V symbolrepresents: a linear or branched alkyl radical having from 5 to 20carbon atoms; a radical of formula —(CH₂)_(p)—COO—R¹² wherein prepresents a number from 5 to 20 and R¹² represents a linear or branchedalkyl radical having from 1 to 12 carbon atoms; a radical of formula—(CH₂)_(q)—O—R¹³ wherein q represents a number from 3 to 10 and R¹³represents a hydrogen atom, an ethylene oxide sequence, a propyleneoxide sequence, a mixed ethylene oxide+propylene oxide sequence or anacyl radical having from 2 to 12 carbon atoms; c is a number chosen from0, 1 and 2; d is a number chosen from 0, 1 and 2; and c+d is at mostequal to
 2. 25. The composition according to claim 23, wherein thepolyorganosiloxane (VIII) further comprises other siloxyl unit(s) offormula: $\begin{matrix}{(R)_{e}(X)_{f}{{Si}(O)}_{\frac{4 - {({e + f})}}{2}}} & ({IV})\end{matrix}$ wherein: R and X have the same meanings as those givenwith respect to the formula (I); e is a number chosen from 0, 1, 2 and3; f is a number chosen from 0, 1, 2 and 3; and e+f is at most equal to3.
 26. The composition according to claim 23, wherein thepolyorganosiloxane (VIII) is a linear polydiorganosiloxane of meanformula:

wherein: the R, Z and V symbols have the meanings given above withrespect to the formulae (I) and (III); the Y symbol represents amonovalent radical chosen from the R, Z, V and X radicals; the R¹⁴symbols are identical or different and represent a monovalent radicalchosen from an R radical and an X radical as defined above with respectto the formula (I); and r, s and t are equal to zero or representintegers or fractional numbers of greater than zero, with the furtherproviso that, if r=0, at least one of the two Y radicals represents theZ radical.
 27. The composition according to claim 21, wherein thecompound (VIII) corresponds to the following formula:

wherein: x″ is between 0 and 1000, y″ is between 1 and 50, and with aproportion by weight of the compound of formula (VI) in the compositionoptionally being between 0.2 and 5%.
 28. The composition according toclaim 21, wherein the polyorganosiloxane (I) exhibits units of formula:$\begin{matrix}{W_{a}Z_{b}^{\prime}{Si}\quad O_{\frac{4 - {({a + b})}}{2}}} & ({VII})\end{matrix}$ wherein: W is an alkenyl group, preferably a vinyl orallyl group, Z′ is a monovalent hydrocarbonaceous group having nounfavourable effect on the activity of the catalyst and is optionally analkyl group having from 1 to 8 carbon atoms inclusive, or an aryl group,a is 1 or 2, b is 0, 1 or 2, and a+b is between 1 and 3, and optionally,at least a portion of the other units being units of mean formula:$\begin{matrix}{Z_{c}^{\prime}{Si}\quad O_{\frac{4 - c}{2}}} & ({VIII})\end{matrix}$ wherein Z′ has the same meaning as above and c has a valueof between 0 and
 3. 29. The composition according to claim 21, whereinthe polyorganosiloxane (II) comprises siloxyl units of formula:$\begin{matrix}{H_{d}L_{e}{Si}\quad O_{\frac{4 - {({d + e})}}{2}}} & ({IX})\end{matrix}$ wherein: L is a monovalent hydrocarbon group having nounfavourable effect on the activity of the catalyst and optionally beingan alkyl group having from 1 to 8 carbon atoms inclusive, or an arylgroup, d is 1 or 2, e is 0, 1 or 2, and d+e has a value of between 1 and3, and optionally, at least a portion of the other units being units ofmean formula: $\begin{matrix}{L_{g}{Si}\quad O_{\frac{4 - g}{2}}} & (X)\end{matrix}$ wherein L has the same meaning as above and g has a valueof between 0 and
 3. 30. The composition according to claim 21, whereinthe promoter (IV) comprises: (IV.1) at least one alkoxylatedorganosiloxane having, per molecule, at least one C₂-C₆ alkenyl group,(IV.2) at least one organosilicon compound having at least one epoxyradical, and (IV.3) at least one metal M chelate or one metal alkoxideof general formula: M(OJ)_(n), with n is the valency of M and J is alinear or branched C₂-C₆ alkyl.
 31. The composition according to claim30, wherein the alkoxylated organosiloxane (IV.1) of the promoter (IV)corresponds to the following general formula:

wherein: R″¹, R′² and R′³, identical or different, are hydrogen orhydrocarbon radicals, A is a linear or branched C₁-C₄ alkylene or adivalent group of formula —CO—O-alkylene, where the alkylene group is asdefined above and the valency is bonded to the Si via G, L is a valencybond or oxygen, R′⁴ and R′⁵ are identical or different radicals andrepresent a linear or branched C₁-C₄ alkyl, x′=0 or 1, and x=0 to
 4. 32.The composition according to claim 30, wherein the organosiliconcompound (IV.2) of the promoter (IV) is: a product (IV.2a) of followinggeneral formula:

wherein: R′⁶ is a linear or branched C₁-C₄ alkyl radical, R′⁷ is alinear or branched alkyl radical, y is equal to 0, 1, 2 or 3, and X′ isequal to:

wherein: E and D identical or different radicals are linear or branchedC₁-C₄ alkylenes, z is equal to 0 or 1, R′⁸, R′⁹ and R′¹⁰ identical ordifferent represent hydrogen or a linear or branched C₁-C₄ alkyl,optionally, R′⁸, R′⁹ and R′¹⁰ constitute, together with the two carbonscarrying the epoxy, an alkyl ring having from 5 to 7 ring members, or aproduct (IV.2b) being an epoxyfunctional polydiorganosiloxane having atleast one unit of formula: $\begin{matrix}{X_{p}^{\prime}G_{p}{Si}\quad O_{\frac{4 - {({p + q})}}{2}}} & ({XIII})\end{matrix}$ wherein: X′ is the radical as defined above for theformula (XII), G is a monovalent hydrocarbon group which has nounfavourable effect on the activity of the catalyst and which is analkyl group having from 1 to 8 carbon atoms inclusive, or an aryl group,p=0, 1 or 2, q=1, 2 or 3, p+q=0, 1, 2 or 3, and optionally at least aportion of the other units of these polydiorganosiloxanes being units ofmean formula: $\begin{matrix}{G_{r}{Si}\quad O_{\frac{4 - r}{2}}} & ({XIV})\end{matrix}$ wherein G has the same meaning as above and r has a valueof between 0 and
 3. 33. The composition according to claim 30, whereinthe metal M of the chelate or of the alkoxide (IV.3) is Ti, Zr, Ge, Lior Mn.
 34. The composition according to claim 21, wherein the adhesionpromoter comprises: vinyltrimethoxysilane (VTMO)(IV.1),3-glycidoxypropyltrimethoxysilane (GLYMO)(IV.2), and butyl titanate(IV.3).
 35. The composition according to claim 21, wherein theunsaturated resin (VII) comprises at least one vinyl per molecule andcorresponds to the following formulae:MM^(Vi)DD^(Vi)Q  (XV),MD^(Vi)Q  (XVI) orMM^(Vi)Q  (XVII).
 36. The composition according to claim 30, comprisingthe constituents (I) to (VIII), as % by weight on a dry basis withrespect to the total weight: (I) 1 to 80 (II) 0.1 to 20 (III) 0.0002 to0.04 (IV.1) 0.01 to 5 (IV.2) 0.01 to 5 (IV.3) 0.01 to 3 (V) 0 to 90 (VI)0 to 0.5 (VII) 0 to 80, and (VIII) 0.2 to
 5. 37. The compositionaccording to claim 36, wherein the % by weight on a dry basis withrespect to the total weight are: (I) 10 to 60 (II) 0.5 to 10 (III)0.0005 to 0.02 (IV.1) 0.05 to 2 (IV.2) 0.05 to 2 (IV.3) 0.1 to 1 (V) 10to 80 (VI) 0.005 to 0.3 (VII) 5 to 70, and (VIII) 0.5 to
 2. 38. Atwo-component precursor system of the composition as defined in claim21, comprising: two separate parts A and B intended to be mixed to formthe composition, said parts A and B comprising the catalyst (III) and asingle polyorganosiloxane entity (I) or (II), the part A or B comprisingthe compound (IV.1) of the promoter (IV) does not comprise the catalyst(III), the resin (VII) being in the part A or the part B or in bothparts A and B, the part A or B comprising the POS (II) and the resin(VII) being devoid of catalyst (III), and the thixotropic compound(VIII) being in the part A or B comprising the catalyst (III).
 39. Anadhesive bonding of components for the construction of motor vehicles,and for the construction of domestic electrical appliances comprising acomposition as defined in claim
 21. 40. A molding crosslinkable adhesivesilicone composition comprising a composition as defined in claim 21.